Conventional image forming apparatuses exploiting electrophotography such as copiers, printers, etc., incorporate an optical scanning device that scans and thereby irradiates the surface of a photosensitive drum which has been electrostatically charged uniformly by a charging device with laser light modulated based on entered image data. An electrostatic latent image formed by the optical scanning device is developed into a toner image by a developing device. Then, the toner image is transferred to a recording sheet or the like, and is then turned into a permanent image by a fixing device. In this way, an image forming process proceeds.
The optical scanning device includes a laser light source (LD) that emits laser light for writing an electrostatic latent image, an optical system for scanning, while reflecting the emitted laser light, in the axial direction (the main scanning direction) of the photosensitive drum, a housing for housing these, a light source circuit board fitted to the housing, etc. The optical scanning device writes an electrostatic latent image on the surface of the photosensitive drum with laser light with which the optical system scans the surface.
For example, Patent Document 1 discloses an optical scanning device that includes four laser light sources, an optical system for scanning with laser light, and four light source circuit boards for controlling the output of the laser light sources respectively. For another example, Patent Document 2 discloses an optical scanning device that includes four laser light sources, an optical system for scanning with laser light, and one light source circuit board for controlling the output of four laser light sources.